How to write a bootable ISO Windows installation disk to a disk partition (and not USB flash drive)?

I have already read How to write bootable iso to a partition? and How do I place a bootable ISO on a USB drive?, but here it's a bit different:

I'd like to put the Windows 10 (or 7) bootable ISO installation disk into an external disk partition (and not into a USB flash drive). How to do this?

More generally, how to write a bootable ISO to a disk partition with Windows?

Notes:

• The latter is important because the main solutions of How do I place a bootable ISO on a USB drive? don't work: Rufus, for example, doesn't offer the possibility to do it on a hard drive partition (I just tried now, the "Device" list is empty ; when I insert a USB flash drive, here it works)




• If possible, I'd like to install the bootable Windows 10 installer ISO into (bootable) Partition 2 of a disk. Partition 1 of the same disk is where Windows will be eventually installed ; once it will be installed, I will be able to delete this no-longer needed Partition 2.

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Why to do this? Here's the reason: I've installed Windows many many times, but at the end it's always slow from a USB flash drive. A nice solution would be: put the ISO installer on Partition 2 of the actual disk where it's going to be installed, then boot on this Partition 2, and install Windows on Partition 1. Then you can remove Partition 2. It should be very fast, in the case it's a SSD for example.